Tolfenamic acid
CLINICAL USE
NSAID: Treatment of migraine
DOSE IN NORMAL RENAL FUNCTION
200 mg when first symptoms appear; repeat once after 1–2 hours if satisfactory response is not obtained
PHARMACOKINETICS
Molecular weight : 261.7 %Protein binding : >99 %Excreted unchanged in urine : 8 (90% as metabolites) Volume of distribution (L/kg) : 0.16 half-life – normal/ESRD (hrs) : 2.5 DOSE IN RENAL IMPAIRMENT
GFR (mL/MIN)
20 to 50 : Dose as in normal renal function 10 to 20 : Use with cution and monitor renal function <10 : Avoid DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
CAPD : Removal unlikely. Use with caution HD : Not dialysed. Use with caution HDF/high flux : Unknown dialysability. Use with caution CAV/VVHD : Unlikely to be dialysed. Use with caution IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugs ACE inhibitors and angiotensin-II antagonists: antagonism of hypotensive effect; increased risk of nephrotoxicity and hyperkalaemia Analgesics: avoid concomitant use of 2 or more NSAIDs, including aspirin (increased side effects); avoid with ketorolac (increased risk of side effects and haemorrhage) Antibacterials: possibly increased risk of convulsions with quinolones Anticoagulants: effects of coumarins enhanced; possibly increased risk of bleeding with heparins and coumarins Antidepressants: increased risk of bleeding with SSRIs and venlafaxine Antidiabetic agents: effects of sulphonylureas enhanced Anti-epileptics: possibly increased phenytoin concentration Antivirals: increased risk of haematological toxicity with zidovudine; concentration possibly increased by ritonavir Ciclosporin: may potentiate nephrotoxicity Cytotoxic agents: reduced excretion of methotrexate; increased risk of bleeding with erlotinib Diuretics: increased risk of nephrotoxicity; antagonism of diuretic effect; hyperkalaemia with potassium-sparing diuretics Lithium: excretion decreased Pentoxifylline: increased risk of bleeding Tacrolimus: increased risk of nephrotoxicity ADMINISTRATION
Reconstition
– Route
Oral Rate of Administration
– Comments
– OTHER INFORMATION
Contraindicated in significantly impaired kidney or liver function The urine may become a little more lemon-coloured due to coloured metabolites Use only with extreme caution (or not at all) in haemodialysis patients with some degree of urine output, especially if other risk factors are present, e.g. nephrotic syndrome or diabetes mellitus or treatment with loop diuretics Use normal doses in patients with CKD 5 on dialysis as long as they no longer pass any urine Inhibition of renal prostaglandin synthesis by NSAIDs may interfere with renal function, especially in the presence of existing renal disease – avoid NSAIDs if . ToLFEnAMiC ACid 737 possible; if not, check serum creatinine 48–72 hours after starting NSAID – if increased, discontinue therapy Use with caution in renal transplant recipients as can reduce intrarenal autocoid synthesis .
See how to identify renal failure stages according to GFR calculation
See how to diagnose irreversible renal disease
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